Educational disclaimer: This article is intended for educational purposes only. It summarizes published research and does not constitute medical advice, a treatment recommendation, or an endorsement of any product. Cannabinoid products, including cannabidiol (CBD) and tetrahydrocannabinol (THC), can interact with medications commonly used in Parkinson's disease and may cause side effects. Readers should talk with their neurologist or treating physician before making any changes to their care plan or before using any cannabinoid product.
Interest in cannabis and cannabinoid compounds among people living with Parkinson's disease has grown substantially over the past decade, driven in part by wider legal access to medical and recreational cannabis and by patient interest in options for symptoms that are not always well controlled by standard therapies. A separate article in this series discusses the endocannabinoid system and its proposed role in Parkinson's disease biology in more depth. This piece focuses specifically on what patient surveys and clinical studies have reported about symptom-related use, effects, and safety. As described below, the available evidence is preliminary, drawn largely from small and short-duration studies, and researchers who conduct this work consistently call for larger, controlled trials before any firm conclusions can be drawn.
What Patient Surveys Report About Self-Reported Cannabis Use
Several survey-based studies have asked people with Parkinson's disease directly about their cannabis use, and these surveys offer a picture of real-world patterns rather than controlled outcomes. A structured interview study of 47 patients treated with medical cannabis for at least three months found that a large majority reported subjective improvement in overall symptoms, with respondents describing reductions in pain, stiffness, and tremor along with improvements in mood and sleep quality [1]. Because this study relied on retrospective patient recall rather than blinded assessment, the authors themselves noted it could not establish whether these changes reflected a true pharmacological effect, a placebo response, or other factors.
A larger web-based survey of people with Parkinson's disease and multiple sclerosis found that a substantial proportion of respondents with Parkinson's disease reported current cannabis use, with users describing perceived benefits related to mood, memory, and fatigue [2]. A more recent nationwide United States survey of people with Parkinson's disease, published in npj Parkinson's Disease, similarly found that the most common reasons cited for cannabis use were non-motor symptoms, particularly anxiety, pain, and sleep disturbance, and that cannabis users were more likely than non-users to report that their non-motor symptoms were inadequately controlled by their prescribed medications [3]. That same survey found that a portion of users discontinued cannabis within six months, most commonly because they did not perceive a benefit, and that a majority of non-users cited a lack of scientific evidence as their reason for avoiding it. Taken together, these surveys indicate that sleep, pain, anxiety, and to a lesser extent tremor and general motor symptoms are the symptoms patients most often associate with their reasons for trying cannabis, but survey data of this kind is inherently limited by self-report bias, the absence of a control group, and the possibility that people who perceive benefit are more likely to respond to a survey in the first place.
Small Clinical Studies on Motor Symptoms
Beyond surveys, a small number of clinical studies have attempted to measure cannabinoid effects on Parkinson's disease symptoms using more structured methods, though nearly all of them involve very small numbers of participants. An open-label observational study conducted in Israel followed patients with Parkinson's disease before and after cannabis use and reported improvement in motor scores on the Unified Parkinson's Disease Rating Scale, along with reported improvements in specific motor symptoms such as tremor, rigidity, and bradykinesia, as well as sleep and pain scores [4]. The authors were explicit that this was an open-label design without a placebo comparison, meaning that expectation effects could not be ruled out, and they called for larger, controlled studies to confirm the findings.
Earlier work examined levodopa-induced dyskinesia specifically. A small randomized, double-blind, placebo-controlled crossover pilot study of the synthetic cannabinoid nabilone in seven patients reported a reduction in dyskinesia severity during the treatment period [5]. This was among the first controlled trials in this area, but its very small sample size limits how confidently its results can be generalized, and later research has produced mixed results regarding cannabinoids and dyskinesia.
CBD specifically has also been studied for motor symptoms, generally with modest or inconclusive results. A widely cited exploratory double-blind trial gave CBD at a dose of 300 milligrams per day to a small group of Parkinson's disease patients without dementia or psychiatric comorbidities; this study did not find a significant effect on motor function scores, though it reported an improvement in a measure of quality of life among participants [6]. Because the sample size was small and the trial was short in duration, the authors described their findings as preliminary and emphasized the need for larger trials with longer follow-up.
Research on Non-Motor Symptoms: Sleep, Anxiety, and Psychosis-Related Symptoms
Non-motor symptoms have been a particular focus of recent cannabinoid research in Parkinson's disease, consistent with what patient surveys suggest about motivations for use. The same exploratory CBD trial mentioned above also assessed REM sleep behavior disorder, a common non-motor feature of Parkinson's disease, and reported improvement in this measure among a subset of participants, without significant side effects noted during the trial period [6]. Because REM sleep behavior disorder was a secondary outcome examined in only a handful of patients, this finding is considered preliminary and has not been confirmed in larger controlled trials.
Nabilone has also been studied specifically for non-motor symptoms in a randomized, placebo-controlled, double-blind trial using an enriched enrollment withdrawal design, a method intended to identify responders before formal randomization. This trial, known as the NMS-Nab study, found reductions in non-motor symptom burden with nabilone compared to placebo, with effects reported particularly on measures related to anxiety and sleep disturbance [7]. The study's authors described the trial as a single-center, phase II study and noted that its findings would need to be replicated in larger, multi-center trials before nabilone could be considered an established option for non-motor symptoms in Parkinson's disease.
Psychosis-related symptoms, including hallucinations, have also drawn research interest, given that these symptoms are a known complication of Parkinson's disease and of some dopaminergic medications used to treat it. A small open-label pilot study gave CBD to six patients with Parkinson's disease who had experienced psychosis for at least three months and reported a decrease in psychotic symptom scores without worsening of motor function [8]. This was an uncontrolled study with a very small number of participants, and the authors were careful to characterize it as preliminary, noting that placebo-controlled trials with larger samples were needed before conclusions about efficacy could be drawn. It is also worth noting that other case reports in the literature describe cannabis use triggering or worsening hallucinations in some people with Parkinson's disease, underscoring that individual responses appear to vary and that this remains an area of active and sometimes conflicting research.
Safety, Tolerability, and Drug Interaction Considerations
Safety and tolerability data specific to Parkinson's disease populations remain limited but are beginning to accumulate. An open-label, dose-escalation study of purified CBD in people with Parkinson's disease and significant rest tremor reported that all participants experienced at least one adverse event during the study, most commonly diarrhea, somnolence, and fatigue; the study also noted elevations in liver enzymes at higher doses, a finding the researchers flagged as clinically relevant and worth monitoring [9]. Adverse events in this study were generally described as mild, but the authors emphasized that their results applied to a specific pharmaceutical-grade CBD formulation at specific doses and cautioned against generalizing to other CBD products, which vary widely in composition and purity.
Because Parkinson's disease is typically managed with multiple medications, including levodopa, dopamine agonists, and monoamine oxidase-B inhibitors, drug interaction considerations are relevant to any discussion of cannabinoid use in this population. Cannabinoids are metabolized by cytochrome P450 liver enzymes that also metabolize many other drugs, and a systematic review of clinical drug interactions with cannabis identified a number of medication classes, including certain anticoagulants and immunosuppressants, where interactions have been documented with varying levels of clinical risk [10]. While this review was not specific to Parkinson's disease medications, its findings illustrate why pharmacological interactions are a legitimate consideration, and why clinicians generally recommend that any person taking prescription medications discuss cannabinoid use with their care team before starting, so that potential interactions and side effects can be monitored appropriately.
The Overall State of the Evidence
Across surveys and clinical studies alike, several limitations recur throughout this body of research. Sample sizes in the clinical trials described here range from single digits to several dozen participants, far smaller than the hundreds or thousands typically enrolled in trials that lead to approved therapies. Study durations are generally short, often just weeks, which leaves open questions about longer-term effects and durability of any observed changes. Several of the studies discussed were open-label, meaning participants and researchers knew what treatment was being given, which introduces the possibility of placebo response or expectation bias affecting reported outcomes. Survey-based research adds further limitations related to self-report and the likelihood that people with strong opinions, positive or negative, may be more inclined to participate. Researchers across this literature have been consistent in describing their own findings as preliminary or exploratory and in calling for larger, adequately powered, randomized, placebo-controlled trials with longer follow-up before conclusions can be drawn about whether cannabinoids meaningfully affect the course or symptoms of Parkinson's disease. At this stage, the research should be understood as an active and evolving area of study rather than as established clinical guidance.
Educational disclaimer: As noted above, this article is provided for educational purposes only and summarizes published research; it is not medical advice and should not be used to guide treatment decisions. Cannabinoid products may interact with Parkinson's disease medications and can cause side effects, and their quality and composition are not consistently regulated. Anyone considering the use of a cannabinoid product should speak with their neurologist or treating physician first, so that any potential risks, interactions, or monitoring needs can be discussed in the context of their individual care plan.
References
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Kindred JH, Li K, Ketelhut NB, et al. Cannabis use in people with Parkinson's disease and Multiple Sclerosis: A web-based investigation. Complementary Therapies in Medicine. 2017;33:99-104. https://pubmed.ncbi.nlm.nih.gov/28735833/
Feeney MP, Bega D, Kluger BM, et al. Weeding through the haze: a survey on cannabis use among people living with Parkinson's disease in the US. npj Parkinson's Disease. 2021;7:21. https://pubmed.ncbi.nlm.nih.gov/33658517/
Lotan I, Treves TA, Roditi Y, Djaldetti R. Cannabis (medical marijuana) treatment for motor and non-motor symptoms of Parkinson disease: an open-label observational study. Clinical Neuropharmacology. 2014;37(2):41-44. https://pubmed.ncbi.nlm.nih.gov/24614667/
Sieradzan KA, Fox SH, Hill M, Dick JP, Crossman AR, Brotchie JM. Cannabinoids reduce levodopa-induced dyskinesia in Parkinson's disease: a pilot study. Neurology. 2001;57(11):2108-2111. https://pubmed.ncbi.nlm.nih.gov/11739835/
Chagas MH, Zuardi AW, Tumas V, et al. Effects of cannabidiol in the treatment of patients with Parkinson's disease: an exploratory double-blind trial. Journal of Psychopharmacology. 2014;28(11):1088-1098. https://journals.sagepub.com/doi/10.1177/0269881114550355
Peball M, Krismer F, Knaus HG, et al. Nabilone for non-motor symptoms of Parkinson's disease: a randomized placebo-controlled, double-blind, parallel-group, enriched enrolment randomized withdrawal study (The NMS-Nab Study). Journal of Neural Transmission. 2019;126(8):1061-1072. https://pubmed.ncbi.nlm.nih.gov/31129719/
Zuardi AW, Crippa JAS, Hallak JEC, et al. Cannabidiol for the treatment of psychosis in Parkinson's disease. Journal of Psychopharmacology. 2009;23(8):979-983. https://pubmed.ncbi.nlm.nih.gov/18801821/
Leehey MA, Liu Y, Hart F, et al. Safety and Tolerability of Cannabidiol in Parkinson Disease: An Open Label, Dose-Escalation Study. Cannabis and Cannabinoid Research. 2020;5(4):326-336. https://pubmed.ncbi.nlm.nih.gov/33381646/
Lopera V, Rodríguez A, Amariles P. Clinical Relevance of Drug Interactions with Cannabis: A Systematic Review. Journal of Clinical Medicine. 2022;11(5):1154. https://pmc.ncbi.nlm.nih.gov/articles/PMC8911401/